Pilot light for ovens



Patented Mar. 28,1939 I "mrao PHD! LIGHT FOR @VENQ Edwin H. Lockwood,Mansfield, om, assignor m Westinghouse Electric & Manufacturing Company,East Pittsburgh, Pa, a corporation or Application Ferm -yer, ices, (or.177-811) It is a further object of this invention'to indicate thecondition ,or a thermostat controlling the oven so that the operatorshall not be required to listen for the cllcls oi the thermostat when itis changing connections.

It is a further object of this invention to provide such an indicatorwhich will operate in all on positions of the operating switch.

Other objects or the invention and details of the proposed constructionwill be apparent irom the iollowingdescrlption and the accompanyingdrawing, in which the single figure is a. circuit diagram illustratingthe apparatus and connections used in this invention.

In the dia, power mains I and 2 and neutral wire 3 of the three-wiresystem are shown.

A switch is provided which I have illustrated by means of a diagramincluding a cam t. This illustration is not restrictive. Any switchwhich will make the described connections may be used. No invention inthe switch per 'se is the subject of this application.

A connection 3 from the main wire i to the blade s of the switch iscontinued, when the cam d has been rotated to close the switch 8,through the wire l to one terminal e of the thermostat. This occurs whenthe com d has been rotated clockwise until the mark comes into theposition opposite the reference mark indicated as an arrow. The mark 03"is shown as opposite said reference mark in the drawing.

A connection it from the wire 2 to the switch blade 9 is continued, whenthe switch is closed, over wire ii to the heater it in the bottom oi theoven, and from the heater 6% a wire It extends to a terminal it of thethermostat. The heater it is located near the bottom of the oven,which'is diagrammatically indicated by the rectangle 85.

Another blade operated by a separate proiection on the cam is shown atIt. and controls aconnection from the wire ill to the wire it which goesto the top heater ll of the oven and tromthere a wire It extends to aterminal it of the thermostat. Between the terminal i9 and the terminal8, the thermostat has a conducting block which is connected by wire '28to a lamp 2! and thence through a wire it to the neutral wire 8.

i No. 86.01!

The thermostat as illustrated is of the familiar snap-action disc type,but any suitable form of thermostat may be used. The disc 28 isillustrated in its composition. when heated, this disc moves with a snapaction to a position 5 in which all the circuits controlled thereby areopened. The mechanical details or the way this is done are illustrativeonly and are intended merely to indicate the control of the circuits bythe thermostat. I is The terminal it, when the thermostat is incircuit-closing position, is connected by the bridging-piece 26 to ablock dl. Similarly, the bridgins-piece it connects the terminal it withthe block it, when the disc is in the illustrated posi- 1s tion, and atthe same time the bridging piece 29 connects the block it to theterminal 8. A resistor 30, which acts as a radiant heating coil tonarrow the temperature difierential of the thermostat, is connectedbetween the block 2? and 20 the terminal i9.

In the operation of the device, when the cam d is rotated clockwise fromthe illustrated position to the position in which BA is uppermost.(opposite the reference arrow) the switches 6 5 and 9 are closed andswitch it is open. A circult is then established from the main wire iover the wire 5, switch blade 5, wire l, terminal 8,. bridging-piece 29,block 26, wire 2i, lamp 22 and wire 23 to the neutral wire 3.

A circuit is also established over the wire iii. switch blade 9, wineii, bottom heater i2. wire it, terminal is, bridging-piece it, block 2i,resistor 3t, te it, bridging-piece it to block 2d, brldging piece 2t,terminal 8, wire I, switch as t and wire 5 to the main wirei.

It will thus be seen that with the cam. t in the position described, thebottom heater i2 is connected between the main wire 2 and the main wire8. It is also connected through the so lamp 22 to the neutral 8. The topheater ii is disconnected. the switch blade is being in opencircuitposition. This position of the cam switch 6 is the position used forbaking. It gives a medium heat.

When the cam 5 is being movedto the BA position it passes through theposition in which the mark PH is opposite the reference mark. Ii it bestopped in this PH position, the switches 9,

t and it are all closed. The circuit is through a as and from there toblock as. From cs the block 20 both of these circuits are completed overbridging-piece 28 and switch 6 to the other main wire I. The lamp 22 isalso energized by reason of the diflerence in potential between block 20and neutral wire 3.

The position of the cam is for preheating. It isthe position used whenthe oven is first energized, and its purpose is to bring the ovenquickly to the desired temperature. Afterthe oven has reached thedesired temperature, the cam is turned to one of the other positions.

It the switch be turned until the mark BR is at the index point, theswitches 6 and i5 are closed and the switch 8 is open. There is thenestablished a circuit from main wire 2 over wire i0, switch l5, wire I6,top heater I'I, wire i8, terminal l9 and bridgin -piece 28, the block20, bridging piece 29, terminal 8, wire I, switch 6 and wire 5 to mainwire I. There is again a connection from block 20 through the lamp 22 tothe neutral wire 3. y

This is the broiling position in which a medium heat diil'ering indegree from the before-mentioned medium heat is obtained. The differencein degree of these two medium-heat positions is eflective even when theenergy for which the two heaters l2 and I! are designed to be equal,because one of these two is farther from the object to be heated thanthe-other. The broiling is obtained by placing the article to be heatednear the top of the oven, and, the top heater being close thereto, thecooking is by radiant heat. In the baking position. of the switch, thecooking is principally done with heated air heated and circulated by thebottom heater.

It will be observed that the lamp 22 is in the connection from block 20to the neutral wire and that this connection does not include any of thecam-operated switches. Moreover, the connection from main wire I toblock 20 does not include any of the heaters. When any of the heatersare working, therefore, block In is at a different potential fromneutral wire 3 and the lamp 22 will shine. The connections hereintracedfrom main 2 through one or both heaters to the block 20 are, whenthe thermostat is closed, equivalent to a connection, not to the neutralwire 3, but to the main I because of the difllerence of potential justmentioned. Only when the thermostat has opened is the lamp extinguished.It is thus a reliable indication of when the oven is drawing current.

It will be evident to those skilled in the art that many modificationsmay be introduced without departure irom the spirit of this invention,and I desire that the diagram and description shall be considered asillustrative only.- The invention is not limited, except by the expresslimitations in the claims or as required by the prior a1 I claim as myinvention:

1. The combination with a three-wire circuit including two main wiresand a neutral wire, of a pair of current-consuming devices, meansincluding a control switch, a manual switch ior selectively connectingsaid devices to one of said main lines and for effecting connection ofthe control switch to the other main line, an indicator, and meansincluding said control switch for connecting both said devices and onetenninal of said indicator to said other line through said manualswitch, the other terminal of said indicator being connected to saidneutral wire.

2. The combination with a three-wire circuit including two main wiresand a neutral wire, of

a plurality of current-consuming devices, first switch means, meansincluding second switch means for selectively connectingsaid devices toone of said main lines and for effecting connection of said first switchmeans to the other main line, an indicator, and means including saidfirst switch means for connecting said devices and one terminal of saidindicator to said other line through said second switch means, the otherterminal of said indicator being connected to said neutral wire.

3. The combination with a three-wire circuit including two main wiresand a neutral wire, 0! a plurality of heating elements, control meansopening in response to predetermined temperature conditions, meansincluding switch means for selectively connecting said elements to oneof said main lines and for effecting connection of said control means,when closed, to the other main line, an indicator, and means includingsaid control means, when closed, to! connecting said heaters and oneterminal of said indicator to said other main line through said switchmeans, the other terminal of said indicator being connected to saidneutral wire.

EDWIN H. LOCKWOOD.

